<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>HTMLCSSJS计算器</title>
    <style>
        /* Basic Reset */
        * {
            border: none;
            font-family: 'Open Sans', sans-serif;
            margin: 0;
            padding: 0;
        }
        .center {
            background-color: #fff;
            border-radius: 50%;
            height: 600px;
            margin: auto;
            width: 600px;
        }
        h1 {
            color: #495678;
            font-size: 30px;
            margin-top: 20px;
            padding-top: 50px;
            display: block;
            text-align: center;
            text-decoration: none;
        }
        a {
            color: #495678;
            font-size: 30px;
            display: block;
            text-align: center;
            text-decoration: none;
            padding-top: 20px;
        }
        form {
            background-color: #495678;
            box-shadow: 4px 4px #3d4a65;
            margin: 40px auto;
            padding: 40px 0 30px 40px;
            width: 280px;
        }
        .btn {
            outline: none;
            cursor: pointer;
            font-size: 20px;
            height: 45px;
            margin: 5px 0 5px 10px;
            width: 45px;
        }
        #display {
            outline: none;
            background-color: #98d1dc;
            box-shadow: inset 6px 6px 0px #3facc0;
            color: #dededc;
            font-size: 20px;
            height: 47px;
            text-align: right;
            width: 165px;
            padding-right: 10px;
            margin-left: 10px;
        }
        .number {
            background-color: #72778b;
            box-shadow: 0 5px #5f6680;
            color: #dededc;
        }
        .number:active {
            box-shadow: 0 2px #5f6680;
            -webkit-transform: translateY(2px);
            -ms-transform: translateY(2px);
            -moz-tranform: translateY(2px);
            transform: translateY(2px);
        }
        .operator {
            background-color: #dededc;
            box-shadow: 0 5px #bebebe;
            color: #72778b;
        }
    </style>
</head>

<body>
    <div class="center">
        <a href="https://github.com/guuibayer/simple-calculator" target="_blank"><i class="fa fa-github"></i></a>
        <form name="calculator">
            <input type="button" id="clear" class="btn other" value="C">
            <input type="text" id="display">
            <br>
            <input type="button" class="btn number" value="7" onclick="get(this.value);">
            <input type="button" class="btn number" value="8" onclick="get(this.value);">
            <input type="button" class="btn number" value="9" onclick="get(this.value);">
            <input type="button" class="btn operator" value="+" onclick="get(this.value);">
            <br>
            <input type="button" class="btn number" value="4" onclick="get(this.value);">
            <input type="button" class="btn number" value="5" onclick="get(this.value);">
            <input type="button" class="btn number" value="6" onclick="get(this.value);">
            <input type="button" class="btn operator" value="*" onclick="get(this.value);">
            <br>
            <input type="button" class="btn number" value="1" onclick="get(this.value);">
            <input type="button" class="btn number" value="2" onclick="get(this.value);">
            <input type="button" class="btn number" value="3" onclick="get(this.value);">
            <input type="button" class="btn operator" value="-" onclick="get(this.value);">
            <br>
            <input type="button" class="btn number" value="0" onclick="get(this.value);">
            <input type="button" class="btn operator" value="." onclick="get(this.value);">
            <input type="button" class="btn operator" value="/" onclick="get(this.value);">
            <input type="button" class="btn other" value="=" onclick="calculates();">
        </form>
    </div>
    
    <script>
        document.getElementById("clear").addEventListener("click", function () {
            document.getElementById("display").value = "";
        });
        function get(value) {
            document.getElementById("display").value += value;
        }

        function calculates() {
            var result = 0;
            result = document.getElementById("display").value;
            document.getElementById("display").value = "";
            document.getElementById("display").value = eval(result);
        };
    </script>
</body>

</html>